Synthesis, characterization and thermal behavior of plasticized poly (vinyl chloride) doped with folic acid-modified titanium dioxide.

To inhibit the agglomeration of nanotitanium dioxide, a poly (vinyl chloride) (PVC) composite film doped with folic acid-modified titanium dioxide was synthesized and characterized using X-ray powder diffraction, X-ray photoelectron spectroscopy and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The average grain size of the folic acid-modified titanium dioxide was found to decrease by 1.3 nm, indicating that the cohesiveness of the nanoparticles is decreased. The lowest temperature for 1.0% thermal decomposition of PVC was determined to be 230.0 °C. The decomposition rate at the peak temperature is found to be 39.6% lower than that of a control sample. The stability of the PVC is improved due to a lower number of surface chlorine atoms as well intermolecular attraction. A mechanism for folic acid modification of titanium dioxide-doped PVC is proposed. After doping, the ester groups in the plasticizer show a significant decrease in the vibration peak intensities observed at 1264 cm-1, 1736 cm-1 and 1106 cm-1. The doped PVC film suppresses the release of CO2, and the strongest vibration peak at 1264 cm-1 is found to be 17.2% lower than that for the blank sample, indicating that doping is beneficial for plasticizer recovery.

Kinetics of thermal oxidative degradation of poly (vinyl chloride) containing Ca and Sn at low temperature.

Calcium metal soap and polyol (dipentaerythritol) additives are replacing or partially replacing organotin in poly(vinyl chloride) (PVC) heat stabilizers due to their low cost, nontoxicity and safety. Therefore, investigating the low-temperature thermal oxidative degradation of stabilized plasticized PVC from the source is essential for recycling. This work uses isothermal thermogravimetry to investigate the thermal degradation process and isothermal discoloration of PVC/calcium metal soap/dipentaerythritol/organotin soft products with excellent heat resistance at 453-503 K and under air atmosphere. The chemical kinetics method is used to fit a single equation model of mass loss and time during the thermal oxidation degradation of PVC, and the kinetic equation obtained is: -ln(1 - α) = 3.83 × 103exp (-6834.4/T)t. When the temperature is 453-503 K, the calculation results are basically consistent with the experimental data and are independent of the heating rate and temperature changes. In addition, the isothermal discoloration of different PVC materials was tested under air atmosphere at 468 K. The results show that when the test material is PVC/calcium metal soap/dipentaerythritol/organotin, the heat aging time to become completely blackened is longer than that of the blank sample, which indicates a strong interaction occurs between Sn, Ca and dipentaerythritol complexes and PVC molecules, inhibiting the release of hydrogen chloride. At the same time, in order to recover PVC and prevent it from carbonization, if the temperature is set to 486 K, the thermal oxidation degradation time of PVC should be less than 130 min.

Microwave-assisted direct synthesis of butene from high-selectivity methane.

Methane was directly converted to butene liquid fuel by microwave-induced non-oxidative catalytic dehydrogenation under 0.1-0.2 MPa. The results show that, under microwave heating in a two-stage fixed-bed reactor, in which nickel powder and NiO x -MoOy/SiO2 are used as the catalyst, the methane-hydrogen mixture is used as the raw material, with no acetylene detected. The methane conversion is more than 73.2%, and the selectivity of methane to butene is 99.0%. Increasing the hydrogen/methane feed volume ratio increases methane conversion and selectivity. Gas chromatography/electron impact ionization/mass spectrometry chromatographic analysis showed that the liquid fuel produced by methane dehydrogenation oligomerization contained 89.44% of butene, and the rest was acetic acid, ethanol, butenol and butyric acid, and the content was 1.0-3.0 wt%.

UV-visible spectroscopic study of the salicyladehyde benzoylhydrazone and its cobalt complexes.

Salicyladehyde benzoylhydrazone (SBH) has three groups suitable for forming coordination bond with transition metal. The UV-vis absorption spectra of SBH and its Co(II) complexes in various media were studied by using the deconvolution method. It is found that the structure of complex in solution is different from those in solid crystals. The nature of complexes in solution depends on acidity of the phenolic proton of SBH and on the medium. In neutral or slightly acid medium, the SBH is a non-charged bidentate ligand. And the "free" hydroxyl group on the SBH molecule makes it possible to form hydrogen bonds in solution. In basic medium, the SBH is a mono, negatively charged tridentates ligand.